Semiconductor device

ABSTRACT

A semiconductor device includes a first pillar-shaped silicon layer formed on a planar silicon layer, a gate insulating film formed around the first pillar-shaped silicon layer, a first gate electrode formed around the gate insulating film, a gate line connected to the first gate electrode, a first first-conductivity-type diffusion layer formed in an upper portion of the first pillar-shaped silicon layer, a second first-conductivity-type diffusion layer formed in a lower portion of the first pillar-shaped silicon layer and an upper portion of the planar silicon layer, a first sidewall having a laminated structure of an insulating film and polysilicon and being formed on an upper sidewall of the first pillar-shaped silicon layer and an upper portion of the first gate electrode, and a first contact formed on the first first-conductivity-type diffusion layer and the first sidewall.

RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims the benefit ofthe filing date of Provisional U.S. Patent Application Ser. No.61/648,183 filed on May 17, 2012. The entire content of this applicationis hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a semiconductor device.

2. Description of the Related Art

Semiconductor integrated circuits, particularly integrated circuitsusing MOS transistors, are increasing in integration. With increases inintegration, MOS transistors used in the integrated circuitsincreasingly become finer up to a nano-level. Such finer MOS transistorshave difficulty in suppressing leak currents and difficulty indecreasing areas occupied by circuits in view of the demand for securingnecessary amounts of currents. In order to resolve the problem, thereare proposed surrounding gate transistors (referred to as “SGT”hereinafter) having a structure in which a source, gate, and drain aredisposed perpendicularly to a substrate, and a gate electrode surroundsa pillar-shaped semiconductor layer (for example, refer to JapaneseUnexamined Patent Application Publication Nos. 2-715562, 2-188966, and3-145761).

A conventional SGT manufacturing method includes forming a siliconpillar having a pillar-shaped nitride film hard mask formed thereon,forming a diffusion layer in a lower portion of the silicon pillar,depositing a gate material, planarizing the gate material, etching backthe gate material, and forming an insulating film sidewall on sidewallsof the silicon pillar and the nitride film hard mask. Then, a resistpattern for a gate line is formed, the gate material is etched, thenitride film hard mask is removed, and a diffusion layer is formed in anupper portion of the silicon pillar (for example, refer to JapaneseUnexamined Patent Application Publication No. 2009-182317). Then, anitride film sidewall is formed on the sidewall of the silicon pillar, adiffusion layer is formed in an upper portion of the silicon pillar byion implantation, a nitride film is formed as a contact stopper, anoxide film is formed as an interlayer film, and then contact etching isperformed.

It is known that oxide film etching for forming a contact has a highselection ratio to a nitride film in a flat portion, but the selectionratio in a nitride film shoulder portion is lower than that in the flatportion.

Since the diameter of a silicon pillar of SGT decreases with reductionin size, a flat area is decreased. In addition, a nitride film sidewallcorresponds to a nitride film shoulder portion, and thus the selectionratio of etching an oxide film is decreased. Therefore, etching an oxidefilm to form a contact on a silicon pillar is not stopped by a nitridefilm to form a contact hole which reaches a gate, resulting inshort-circuiting between the silicon pillar and the gate.

There is proposed a structure for preventing the occurrence ofshort-circuiting between a contact and a gate by forming an epitaxialsemiconductor layer on a silicon pillar of SGT (refer to, for example,Japanese Unexamined Patent Application Publication No. 2010-258345).However, epitaxial growth requires insulating film sidewalls to beformed on an upper sidewall of the silicon pillar and on an upperportion of a gate electrode. When polysilicon is used in a gate, siliconis also grown on the gate. Therefore, epitaxial growth to a height equalto or higher than the height of the insulating film sidewall causesshort-circuiting between the gate and an upper portion of the siliconpillar.

On the other hand, the nitride film sidewall is formed on the sidewallof the silicon pillar, and the diffusion layer is formed in an upperportion of the silicon pillar by ion implantation. Therefore, ions areimplanted from above into an upper portion of the silicon pillar, andthus a deep diffusion layer is required to be formed. When a deepdiffusion layer is formed, the diffusion layer is also widened in thelateral direction. That is, higher integration becomes difficult toachieve.

In addition, when the silicon pillar becomes thin, it is difficult toallow impurities to present in the silicon pillar because the silicondensity is 5×10²²/cm³.

It is described that in a flat-type MOS transistor, a sidewall of a LDDregion is composed of polycrystal silicon having the same conductivitytype as a low-concentration layer, and surface carriers of the LDDregion are induced by a difference in work function, thereby decreasingthe impedance of the LDD region as compared an oxide film sidewallLDD-type MOS transistor (refer to, for example, Japanese UnexaminedPatent Application Publication No. 11-297984). It is also described thatthe polycrystal silicon sidewall is electrically insulated from the gateelectrode. Also, drawings show that the polycrystal silicon sidewall isinsulated from source/drain through an interlayer insulating film.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a SGTstructure having a structure for decreasing the resistance of an upperportion of a silicon pillar and a method for manufacturing the SGT.

A semiconductor device according to a first embodiment of the presentinvention includes:

a planar silicon layer formed on a silicon substrate;

a first pillar-shaped silicon layer formed on the planar silicon layer;

a gate insulating film formed around the first pillar-shaped siliconlayer;

a first gate electrode formed around the gate insulating film;

a gate line connected to the first gate electrode;

a first first-conductivity-type diffusion layer formed in an upperportion of the first pillar-shaped silicon layer;

a second first-conductivity-type diffusion layer formed in a lowerportion of the first pillar-shaped silicon layer and in an upper portionof the planar silicon layer;

a first sidewall having a laminated structure of an insulating film andpolysilicon and being formed on an upper sidewall of the firstpillar-shaped silicon layer and on an upper portion of the first gateelectrode; and

a first contact formed on the first first-conductivity-type diffusionlayer and the first sidewall,

wherein the first contact is connected to the polysilicon of the firstsidewall; and

the conductivity type of the polysilicon of the first sidewall is thefirst conductivity type.

The semiconductor device preferably includes a first silicide formed onthe first first-conductivity-type diffusion layer and on the firstsidewall.

The lower surface of the first first-conductivity-type diffusion layeris preferably higher than the upper surface of the first gate electrode.

The first gate electrode preferably has a laminated structure of a metaland polysilicon.

A semiconductor device according to a second embodiment of the presentinvention further includes, in the semiconductor device according to thefirst embodiment:

the planar silicon layer formed on the silicon substrate;

a second pillar-shaped silicon layer formed on the planar silicon layer;

the gate insulating film formed around the second pillar-shaped siliconlayer;

a second gate electrode formed around the gate insulating film;

the gate line connected to the second gate electrode;

a first second-conductivity-type diffusion layer formed in an upperportion of the second pillar-shaped silicon layer;

a second second-conductivity-type diffusion layer formed in a lowerportion of the second pillar-shaped silicon layer and in an upperportion of the planar silicon layer;

a second sidewall having a laminated structure of an insulating film andpolysilicon and being formed on an upper sidewall of the secondpillar-shaped silicon layer and on an upper portion of the second gateelectrode; and

a second contact formed on the first second-conductivity-type diffusionlayer and on the second sidewall,

wherein the second contact is connected to the polysilicon of the secondsidewall; and

the conductivity type of the polysilicon of the second sidewall is thesecond conductivity type.

The semiconductor device preferably includes a first silicide formed onthe first first-conductivity-type diffusion layer and on the firstsidewall, and a second silicide formed on the firstsecond-conductivity-type diffusion layer and on the second sidewall.

The lower surface of the first first-conductivity-type diffusion layeris preferably higher than the upper surface of the first gate electrode,and the lower surface of the first second-conductivity-type diffusionlayer is preferably higher than the upper surface of the second gateelectrode.

The first gate electrode preferably has a laminated structure of a metaland polysilicon, and the second gate electrode preferably has alaminated structure of a metal and polysilicon.

The first sidewall can be formed by depositing the insulating film andthe polysilicon on the first pillar-shaped silicon layer and etching thepolysilicon to leave it as a sidewall.

According to the present invention, contact etching is stopped by thepolysilicon of the first sidewall having a laminated structure includingthe insulating film and the polysilicon and formed on an upper sidewallof the first pillar-shaped silicon layer and an upper portion of thefirst gate electrode. Since the insulating film of the first sidewall isthin and held in the polysilicon, the etching rate is decreased to stopcontact etching by the first sidewall. Therefore, the height from theupper surface of the first first-conductivity-type diffusion layer tothe upper surface of the first gate electrode can be decreased.

Also since the conductivity type of the polysilicon of the firstsidewall is the first conductivity type, surface carriers are induced bya difference in work function, and thus the resistance in an upperportion of a pillar-shaped silicon layer can be decreased. For example,when the first sidewall is n+type, and the pillar-shaped silicon layerhas a low impurity concentration, a transistor composed of the firstsidewall and the pillar-shaped silicon layer is turned on when a voltageapplied to the first sidewall through the contact is 0 V.

As described above, when the lower surface of the firstfirst-conductivity-type diffusion layer is higher than the upper surfaceof the first gate electrode, a channel of the transistor can beelectrically connected to the first first-conductivity-type diffusionlayer.

When an impurity is introduced so that the lower surface of the firstfirst-conductivity-type diffusion layer is higher than the upper surfaceof the first gate electrode, a shallow junction is formed, therebyreducing the widening of the diffusion layer in the lateral direction.That is, higher integration can be realized.

The polysilicon of the first sidewall is formed on an upper sidewall ofthe pillar-shaped silicon layer, and thus the first sidewall has alarger diameter than that of the pillar-shaped silicon layer. Althoughthe pillar-shaped silicon layer becomes thin and thus has difficulty inimplanting impurities in the pillar-shaped silicon layer, impurities canbe implanted into the polysilicon of the first sidewall. Therefore, achannel of the transistor can be electrically connected to the firstfirst-conductivity-type diffusion layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a plan view of a semiconductor device according to anembodiment of the present invention. FIG. 1( b) is a cross-sectionalview taken along line X-X′ in FIG. 1( a). FIG. 1( c) is across-sectional view taken along line Y-Y′ in FIG. 1( a).

FIG. 2( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 2( b)is a cross-sectional view taken along line X-X′ in FIG. 2( a). FIG. 2(c) is a cross-sectional view taken along line Y-Y′ in FIG. 2( a).

FIG. 3( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 3( b)is a cross-sectional view taken along line X-X′ in FIG. 3( a). FIG. 3(c) is a cross-sectional view taken along line Y-Y′ in FIG. 3( a).

FIG. 4( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 4( b)is a cross-sectional view taken along line X-X′ in FIG. 4( a). FIG. 4(c) is a cross-sectional view taken along line Y-Y′ in FIG. 4( a).

FIG. 5( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 5( b)is a cross-sectional view taken along line X-X′ in FIG. 5( a). FIG. 5(c) is a cross-sectional view taken along line Y-Y′ in FIG. 5( a).

FIG. 6( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 6( b)is a cross-sectional view taken along line X-X′ in FIG. 6( a). FIG. 6(c) is a cross-sectional view taken along line Y-Y′ in FIG. 6( a).

FIG. 7( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 7( b)is a cross-sectional view taken along line X-X′ in FIG. 7( a). FIG. 7(c) is a cross-sectional view taken along line Y-Y′ in FIG. 7( a).

FIG. 8( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 8( b)is a cross-sectional view taken along line X-X′ in FIG. 8( a). FIG. 8(c) is a cross-sectional view taken along line Y-Y′ in FIG. 8( a).

FIG. 9( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 9( b)is a cross-sectional view taken along line X-X′ in FIG. 9( a). FIG. 9(c) is a cross-sectional view taken along line Y-Y′ in FIG. 9( a).

FIG. 10( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 10( b)is a cross-sectional view taken along line X-X′ in FIG. 10( a). FIG. 10(c) is a cross-sectional view taken along line Y-Y′ in FIG. 10( a).

FIG. 11( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 11( b)is a cross-sectional view taken along line X-X′ in FIG. 11( a). FIG. 11(c) is a cross-sectional view taken along line Y-Y′ in FIG. 11( a).

FIG. 12( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 12( b)is a cross-sectional view taken along line X-X′ in FIG. 12( a). FIG. 12(c) is a cross-sectional view taken along line Y-Y′ in FIG. 12( a).

FIG. 13( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 13( b)is a cross-sectional view taken along line X-X′ in FIG. 13( a). FIG. 13(c) is a cross-sectional view taken along line Y-Y′ in FIG. 13( a).

FIG. 14( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 14( b)is a cross-sectional view taken along line X-X′ in FIG. 14( a). FIG. 14(c) is a cross-sectional view taken along line Y-Y′ in FIG. 14( a).

FIG. 15( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 15( b)is a cross-sectional view taken along line X-X′ in FIG. 15( a). FIG. 15(c) is a cross-sectional view taken along line Y-Y′ in FIG. 15( a).

FIG. 16( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 16( b)is a cross-sectional view taken along line X-X′ in FIG. 16( a). FIG. 16(c) is a cross-sectional view taken along line Y-Y′ in FIG. 16( a).

FIG. 17( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 17( b)is a cross-sectional view taken along line X-X′ in FIG. 17( a). FIG. 17(c) is a cross-sectional view taken along line Y-Y′ in FIG. 17( a).

FIG. 18( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 18( b)is a cross-sectional view taken along line X-X′ in FIG. 18( a). FIG. 18(c) is a cross-sectional view taken along line Y-Y′ in FIG. 18( a).

FIG. 19( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 19( b)is a cross-sectional view taken along line X-X′ in FIG. 19( a). FIG. 19(c) is a cross-sectional view taken along line Y-Y′ in FIG. 19( a).

FIG. 20( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 20( b)is a cross-sectional view taken along line X-X′ in FIG. 20( a). FIG. 20(c) is a cross-sectional view taken along line Y-Y′ in FIG. 20( a).

FIG. 21( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 21( b)is a cross-sectional view taken along line X-X′ in FIG. 21( a). FIG. 21(c) is a cross-sectional view taken along line Y-Y′ in FIG. 21( a).

FIG. 22( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 22( b)is a cross-sectional view taken along line X-X′ in FIG. 22( a). FIG. 22(c) is a cross-sectional view taken along line Y-Y′ in FIG. 22( a).

FIG. 23( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 23( b)is a cross-sectional view taken along line X-X in FIG. 23( a). FIG. 23(c) is a cross-sectional view taken along line Y-Y′ in FIG. 23( a).

FIG. 24( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 24( b)is a cross-sectional view taken along line X-X′ in FIG. 24( a). FIG. 24(c) is a cross-sectional view taken along line Y-Y′ in FIG. 24( a).

FIG. 25( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 25( b)is a cross-sectional view taken along line X-X′ in FIG. 25( a). FIG. 25(c) is a cross-sectional view taken along line Y-Y′ in FIG. 25( a).

FIG. 26( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 26( b)is a cross-sectional view taken along line X-X′ in FIG. 26( a). FIG. 26(c) is a cross-sectional view taken along line Y-Y′ in FIG. 26( a).

FIG. 27( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 27( b)is a cross-sectional view taken along line X-X′ in FIG. 27( a). FIG. 27(c) is a cross-sectional view taken along line Y-Y′ in FIG. 27( a).

FIG. 28( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 28( b)is a cross-sectional view taken along line X-X′ in FIG. 28( a). FIG. 28(c) is a cross-sectional view taken along line Y-Y′ in FIG. 28( a).

FIG. 29( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 29( b)is a cross-sectional view taken along line X-X′ in FIG. 29( a). FIG. 29(c) is a cross-sectional view taken along line Y-Y′ in FIG. 29( a).

FIG. 30( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 30( b)is a cross-sectional view taken along line X-X′ in FIG. 30( a). FIG. 30(c) is a cross-sectional view taken along line Y-Y′ in FIG. 30( a).

FIG. 31( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 31( b)is a cross-sectional view taken along line X-X′ in FIG. 31( a). FIG. 31(c) is a cross-sectional view taken along line Y-Y′ in FIG. 31( a).

FIG. 32( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 32( b)is a cross-sectional view taken along line X-X′ in FIG. 32( a). FIG. 32(c) is a cross-sectional view taken along line Y-Y′ in FIG. 32( a).

FIG. 33( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 33( b)is a cross-sectional view taken along line X-X′ in FIG. 33( a). FIG. 33(c) is a cross-sectional view taken along line Y-Y′ in FIG. 33( a).

FIG. 34( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 34( b)is a cross-sectional view taken along line X-X′ in FIG. 34( a). FIG. 34(c) is a cross-sectional view taken along line Y-Y′ in FIG. 34( a).

FIG. 35( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 35( b)is a cross-sectional view taken along line X-X′ in FIG. 35( a). FIG. 35(c) is a cross-sectional view taken along line Y-Y′ in FIG. 35( a).

FIG. 36( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 36( b)is a cross-sectional view taken along line X-X′ in FIG. 36( a). FIG. 36(c) is a cross-sectional view taken along line Y-Y′ in FIG. 36( a).

FIG. 37( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 37( b)is a cross-sectional view taken along line X-X′ in FIG. 37( a). FIG. 37(c) is a cross-sectional view taken along line Y-Y′ in FIG. 37( a).

FIG. 38( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 38( b)is a cross-sectional view taken along line X-X′ in FIG. 38( a). FIG. 38(c) is a cross-sectional view taken along line Y-Y′ in FIG. 38( a).

FIG. 39( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 39( b)is a cross-sectional view taken along line X-X′ in FIG. 39( a). FIG. 39(c) is a cross-sectional view taken along line Y-Y′ in FIG. 39( a).

FIG. 40( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 40( b)is a cross-sectional view taken along line X-X′ in FIG. 40( a). FIG. 40(c) is a cross-sectional view taken along line Y-Y′ in FIG. 40( a).

FIG. 41( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 41( b)is a cross-sectional view taken along line X-X′ in FIG. 41( a). FIG. 41(c) is a cross-sectional view taken along line Y-Y′ in FIG. 41( a).

FIG. 42( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 42( b)is a cross-sectional view taken along line X-X′ in FIG. 42( a). FIG. 42(c) is a cross-sectional view taken along line Y-Y′ in FIG. 42( a).

FIG. 43( a) is a plan view of a method for manufacturing a semiconductordevice according to an embodiment of the present invention. FIG. 43( b)is a cross-sectional view taken along line X-X′ in FIG. 43( a). FIG. 43(c) is a cross-sectional view taken along line Y-Y′ in FIG. 43( a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A semiconductor device having a SGT structure according to an embodimentof the present invention is described below with reference to FIG. 1.

A semiconductor device having a SGT structure according to an embodimentof the present invention includes:

a planar silicon layer 107 formed on a silicon substrate 101;

a first pillar-shaped silicon layer 105 formed on the planar siliconlayer 107;

a gate insulating film 109 formed around the first pillar-shaped siliconlayer 105;

a first gate electrode 117 b formed around the gate insulating film 109;

a gate line 117 c connected to the first gate electrode 117 b;

a first n-type diffusion layer 119 formed in an upper portion of thefirst pillar-shaped silicon layer 105;

a second n-type diffusion layer 120 formed in a lower portion of thefirst pillar-shaped silicon layer 105 and in an upper portion of theplanar silicon layer 107;

a first sidewall 201 having a laminated structure of an insulating film127 and polysilicon 115 and being formed on an upper sidewall of thefirst pillar-shaped silicon layer 105 and an upper portion of the firstgate electrode 117 b; and

a first contact 146 formed on the first n-type diffusion layer 119 andthe first sidewall 201,

wherein the first contact 146 is connected to the polysilicon 115 of thefirst sidewall 201; and

the conductivity type of the polysilicon 115 of the first sidewall 201is n-type.

The semiconductor device further includes first silicides 135 and 134formed on the first n-type diffusion layer 119 and the first sidewall201. A silicide satisfactorily stops contact etching because of a highselection ratio for etching an oxide film.

Contact etching is stopped by the polysilicon 115 of the first sidewall201 which has a laminated structure including the insulating film 127and the polysilicon 115 and which is formed on an upper sidewall of thefirst pillar-shaped silicon layer 105 and an upper portion of the firstgate electrode 117 b. Since the insulating film 127 of the firstsidewall 201 is thin and held in the polysilicon 115, the etching rateis decreased to stop contact etching by the first sidewall 201.Therefore, the height from the upper surface of the first n-typediffusion layer to the upper surface of the first gate electrode 117 bcan be reduced.

Also since the conductivity type of the polysilicon of the firstsidewall 201 is n-type, surface carriers are induced by a difference inwork function, and thus the resistance in an upper portion of apillar-shaped silicon layer 105 can be decreased. For example, when thefirst sidewall 201 is n+-type, and the pillar-shaped silicon layer 105has a low impurity concentration, a transistor composed of the firstsidewall 201 and the pillar-shaped silicon layer 105 is turned on when avoltage applied to the first sidewall 201 through the contact 146 is 0V.

As described above, when the lower surface of the first n-type diffusionlayer 119 is higher than the upper surface of the first gate electrode117 b, a channel of the transistor can be electrically connected to thefirst n-type diffusion layer 119.

When impurities are introduced so that the lower surface of the firstn-type diffusion layer 119 is higher than the upper surface of the firstgate electrode 117 b, a shallow junction is formed, thereby reducing thewidening of the diffusion layer in the lateral direction. That is,higher integration can be realized.

The polysilicon of the first sidewall 201 is formed on an upper sidewallof the pillar-shaped silicon layer 105, and thus the first sidewall 201has a larger diameter than that of the pillar-shaped silicon layer 105.Although the pillar-shaped silicon layer 105 becomes thin and thus hasdifficulty in implanting an impurity in the pillar-shaped silicon layer105, an impurity can be implanted into the polysilicon 115 of the firstsidewall 201. Therefore, a channel of the transistor can be electricallyconnected to the first n-type diffusion layer.

The first gate electrode 117 b has a laminated structure of a metal 110and polysilicon 111.

Consequently, SGT has the first sidewall 201 having a laminatedstructure of the insulating film 127 and the polysilicon 115 and formedon an upper sidewall of the first pillar-shaped silicon layer 105 and anupper portion of the first gate electrode 117 b.

CMOS SGT using the SGT according to the embodiment of the presentinvention is described below. The CMOS SGT includes:

a second pillar-shaped silicon layer 104 formed on the planar siliconlayer 107;

the gate insulating film 109 formed around the second pillar-shapedsilicon layer 104;

a second gate electrode 117 a formed around the gate insulating film109;

the gate line 117 c connected to the second gate electrode 117 a;

a first p-type diffusion layer 122 formed in an upper portion of thesecond pillar-shaped silicon layer 104;

a second p-type diffusion layer 123 formed in a lower portion of thesecond pillar-shaped silicon layer 104 and an upper portion of theplanar silicon layer 107;

a second sidewall 202 having a laminated structure of an insulating film126 and polysilicon 114 and being formed on an upper sidewall of thesecond pillar-shaped silicon layer 104 and on an upper portion of thesecond gate electrode 117 a; and

a second contact 145 formed on the first p-type diffusion layer 122 andon the second sidewall 202,

wherein the second contact 145 is connected to the polysilicon 114 ofthe second sidewall 202; and

the conductivity type of the polysilicon 114 of the second sidewall 202is p-type.

The CMOS SGT further includes second silicides 129 and 130 formed on thefirst p-type diffusion layer 122 and the first sidewall 202.

The lower surface of the first p-type diffusion layer 122 is higher thanthe upper surface of the second gate electrode 117 a.

The second gate electrode 117 a has a laminated structure of a metal 110and polysilicon 111.

The second n-type diffusion layer 120 and the second p-type diffusionlayer 123 are connected to each other through a silicide.

The CMOS SGT using the SGT according to the present invention isdescribed above.

A process for manufacturing a semiconductor device having a SGTstructure according to an embodiment of the present invention isdescribed below with reference to FIGS. 2 to 43.

First, as shown in FIG. 2, first resists 102 and 103 are formed forforming the first pillar-shaped silicon layer 105 and the secondpillar-shaped silicon layer 104 on the silicon substrate 101.

Next, as shown in FIG. 3, the silicon substrate 101 is etched to formthe first pillar-shaped silicon layer 105 and the second pillar-shapedsilicon layer 104.

Then, as shown in FIG. 4, the first resists 102 and 103 are removed.

Then, as shown in FIG. 5, a second resist 106 is formed for forming theplanar silicon layer 107.

Then, as shown in FIG. 6, the silicon substrate 101 is etched to formthe planar silicon layer 107.

Then, as shown in FIG. 7, the second resist 106 is removed.

Next, as shown in FIG. 8, an oxide film 108 is deposited and the surfacethereof is planarized.

Then, as shown in FIG. 9, the oxide film 108 is etched to be left aroundthe planar silicon layer 107.

First, as shown in FIG. 10, the gate insulating film 109 is formedaround the first pillar-shaped silicon layer 105 and the secondpillar-shaped silicon layer 104. In this case, an oxide film, alaminated structure of an oxide film and a nitride film, a nitride film,or a high-dielectric film can be used as a material of the gateinsulating film 109.

Next, as shown in FIG. 11, the metal film 110 is formed around the gateinsulating film 109. A metal material which can be used for a gateelectrode, such as titanium, titanium nitride, tantalum, tantalumnitride, or the like, can be used for the metal film 110.

Then, as shown in FIG. 12, polysilicon 111 is deposited and the surfacethereof is planarized.

Then, as shown in FIG. 13, the polysilicon 111 is etched.

Then, as shown in FIG. 14, the polysilicon 111 is etched to expose upperportions of the first pillar-shaped silicon layer 105 and the secondpillar-shaped silicon layer 104.

Then, as shown in FIG. 15, the metal film 110 is etched. In this case,wet etching is preferably used.

Then, as shown in FIG. 16, a thin insulating film 112 and polysilicon113 are deposited.

Then, as shown in FIG. 17, the polysilicon 113 is etched to leave thepolysilicon 114 and 115 as sidewalls on an upper sidewall of the firstpillar-shaped silicon layer 105 and an upper sidewall of the secondpillar-shaped silicon layer 104.

Then, as shown in FIG. 18, a third resist 116 is formed for forming thefirst gate electrode 117 b, the second gate electrode 117 a, and thegate line 117 c.

Then, as shown in FIG. 19, the oxide film 112 is etched.

Then, as shown in FIG. 20, the polysilicon 111, the metal film 110, andthe gate insulating film 109 are etched to form the first gate electrode117 b, the second gate electrode 117 a, and the gate line 117 c.

Then, as shown in FIG. 21, the third resist 116 is removed.

Then, as shown in FIG. 22, a fourth resist 118 is formed for forming thefirst n-type diffusion layer 119 and the second n-type diffusion layer120.

Then, as shown in FIG. 23, arsenic is implanted to form the first n-typediffusion layer 119 and the second n-type diffusion layer 120. At thistime, arsenic is also implanted into the polysilicon 115 of thesidewall. Also, arsenic is implanted into the polysilicon 115 from thesidewall thereof, thereby easily achieving n-type at a highconcentration.

Then, as shown in FIG. 24, the fourth resist 118 is removed.

Then, as shown in FIG. 25, a fifth resist 121 is formed for forming thefirst p-type diffusion layer 122 and the second p-type diffusion layer123.

Then, as shown in FIG. 26, boron is implanted to form the first p-typediffusion layer 122 and the second p-type diffusion layer 123. At thistime, boron is also implanted into the polysilicon 114 of the sidewall.Also, boron is implanted into the polysilicon 114 from the sidewallthereof, thereby easily achieving p-type at a high-concentration.

Then, as shown in FIG. 27, the fifth resist 121 is removed.

Then, as shown in FIG. 28, the nitride film 124 is deposited.

Then, as shown in FIG. 29, heat treatment is performed. In thistreatment, a shallow junction can be formed by decreasing heattreatment. When heat treatment is performed to form a deep junction, thesecond n-type diffusion layer 120 and the second p-type diffusion layer123 are widened in the lateral direction, thereby causing difficulty inincreasing integration.

Then, as shown in FIG. 30, the nitride film 124 is etched, and the oxidefilm 112 is etched to form the nitride film sidewall 125. At the sametime, the first sidewall 201 including the oxide film 127 and thepolysilicon 115 is formed on an upper sidewall of the firstpillar-shaped silicon layer 105, and the second sidewall 202 includingthe oxide film 126 and the polysilicon 114 is formed on an uppersidewall of the second pillar-shaped silicon layer 104.

Then, as shown in FIG. 31, silicide 135, silicide 134, silicide 129, andsilicide 130 are formed on the first n-type diffusion layer 119, thepolysilicon 115, the first p-type diffusion layer 122, and thepolysilicon 114, respectively. In addition, silicides 128, 131, 132,133, and 136 are formed.

Then, as shown in FIG. 32, an interlayer insulating film 137 isdeposited and planarized.

Then, as shown in FIG. 33, a sixth resist 138 is formed for forming thefirst contact 146 and the second contact 145.

Then, as shown in FIG. 34, the interlayer insulating film 137 is etchedto form contact holes 139 and 140. In this case, contact etching isstopped at the polysilicon by the first sidewall having a laminatedstructure of the insulating film and the polysilicon and being formed onan upper sidewall of the first pillar-shaped silicon layer and an upperportion of the first gate electrode. Since the insulating film of thefirst sidewall is thin and held in the polysilicon, the etching rate isdecreased to stop contact etching by the first sidewall.

Then, as shown in FIG. 35, the sixth resist 138 is removed.

Then, as shown in FIG. 36, a seventh resist 141 is formed for formingthe contacts 144 and 147.

Then, as shown in FIG. 37, the interlayer insulating film 137 is etchedto form contact holes 142 and 143.

Then, as shown in FIG. 38, the seventh resist 137 is removed.

Then, as shown in FIG. 39, a metal is deposited to form the contacts 144and 147, the first contact 146, and the second contact 145.

Then, as shown in FIG. 40, a metal 148 is deposited.

Then, as shown in FIG. 41, eighth resists 149, 150, 151, and 152 areformed for forming metal lines 153, 154, 155, and 156.

Then, as shown in FIG. 42, the metal 148 is etched to form the metallines 153, 154, 155, and 156.

Then, as shown in FIG. 43, the eighth resists 149, 150, 151, and 152 areremoved.

What is claimed is:
 1. A semiconductor device comprising: a planarsilicon layer formed on a silicon substrate; a first pillar-shapedsilicon layer formed on the planar silicon layer; a gate insulating filmformed around the first pillar-shaped silicon layer; a first gateelectrode formed around the gate insulating film; a gate line connectedto the first gate electrode; a first first-conductivity-type diffusionlayer formed in an upper portion of the first pillar-shaped siliconlayer; a second first-conductivity-type diffusion layer formed in alower portion of the first pillar-shaped silicon layer and in an upperportion of the planar silicon layer; a first sidewall having a laminatedstructure of an insulating film and polysilicon and being formed on anupper sidewall of the first pillar-shaped silicon layer and on an upperportion of the first gate electrode; and a first contact formed on thefirst first-conductivity-type diffusion layer and the first sidewall,wherein the first contact is connected to the polysilicon of the firstsidewall; and the conductivity type of the polysilicon of the firstsidewall is the first conductivity type.
 2. The semiconductor deviceaccording to claim 1, further comprising a first silicide formed on thefirst first-conductivity-type diffusion layer and on the first sidewall.3. The semiconductor device according to claim 1, wherein the lowersurface of the first first-conductivity-type diffusion layer is higherthan the upper surface of the first gate electrode.
 4. The semiconductordevice according to claim 1, wherein the first gate electrode has alaminated structure of a metal and polysilicon.
 5. The semiconductordevice according to claim 1, further comprising: the planar siliconlayer formed on the silicon substrate; a second pillar-shaped siliconlayer formed on the planar silicon layer; the gate insulating filmformed around the second pillar-shaped silicon layer; a second gateelectrode formed around the gate insulating film; the gate lineconnected to the second gate electrode; a first second-conductivity-typediffusion layer formed in an upper portion of the second pillar-shapedsilicon layer; a second second-conductivity-type diffusion layer formedin a lower portion of the second pillar-shaped silicon layer and anupper portion of the planar silicon layer; a second sidewall having alaminated structure of an insulating film and polysilicon and beingformed on an upper sidewall of the second pillar-shaped silicon layerand an upper portion of the second gate electrode; and a second contactformed on the first second-conductivity-type diffusion layer and thesecond sidewall, wherein the second contact is connected to thepolysilicon of the second sidewall; and the conductivity type of thepolysilicon of the second sidewall is the second conductivity type. 6.The semiconductor device according to claim 5, further comprising afirst silicide formed on the first first-conductivity-type diffusionlayer and the first sidewall, and a second silicide formed on the firstsecond-conductivity-type diffusion layer and the second sidewall.
 7. Thesemiconductor device according to claim 5, wherein the lower surface ofthe first first-conductivity-type diffusion layer is higher than theupper surface of the first gate electrode, and the lower surface of thefirst second-conductivity-type diffusion layer is higher than the uppersurface of the second gate electrode.
 8. The semiconductor deviceaccording to claim 5, wherein the first gate electrode has a laminatedstructure of a metal and polysilicon, and the second gate electrode hasa laminated structure of a metal and polysilicon.
 9. The semiconductordevice according to claim 1, wherein the first sidewall can be formed bydepositing the insulating film and the polysilicon on the firstpillar-shaped silicon layer and etching the polysilicon to leave it as asidewall.